Measurement of the top quark mass in the l+jets channel

Abstract

We present a measurement of the top quark mass using events with one charged lepton (muon or electron) and at least four jets in the final state, collected by CMS in pp collisions at √s=7 TeV. From the full 2010 dataset, corresponding to an integrated luminosity of 36 pb−1, 637 candidate events are selected. The top quark mass is measured to be mt=173.12.1(stat)+2.8−2.5(syst) GeV. A combination with the CMS results obtained in the dilepton channel on the same data sample, yields mt=173.41.9(stat)2.7(syst) GeV.

Main Document

Detailed record in CDS, and the Fulltext in PDF.

Approved Results from TOP-10-009 ( click on plot to get .png )

Result Abbreviated Caption
TheMainResult.PNG Main top mass result, combining the electron+jets and muon+jets channel.
CombinedResult.PNG Combination with the CMS measurement in the di-lepton channel
  See main document for the results in individual electron+jets and muon+jets channels, and for the mass and jet energy scale measured by the cross-check analysis

Approved Plots from TOP-10-009 ( click on plot to get .pdf )

Figure Abbreviated Caption
Missing transverse Energy of the electron+jets selected sample for an integrated luminosity of 36/pb after applying the event selection. GIF
Number of b-tagged jets in the electron+jets selected sample for an integrated luminosity of 36/pb after applying the event selection. GIF
Chi2 from the kinematic fit for the jet assignment that gives the lowest chi2 of the electron+jets selected sample for an integrated luminosity of 36/pb after applying the event selection. GIF
Top quark mass before the fit of the electron+jets selected sample for an integrated luminosity of 36/pb after applying the event selection and requesting at least one solution with chi2<10. GIF
Top quark mass after the fit of the electron+jets selected sample for an integrated luminosity of 36/pb after applying the event selection and requesting at least one solution with chi2<10. GIF
Uncertainty on the fitted top mass of the electron+jets selected sample for an integrated luminosity of 36/pb after applying the event selection and requesting at least one solution with chi2<10. GIF
Missing transverse Energy of the muon+jets selected sample for an integrated luminosity of 36/pb after applying the event selection. GIF
Number of b-tagged jets in the muon+jets selected sample for an integrated luminosity of 36/pb after applying the event selection. GIF
Chi2 from the kinematic fit for the jet assignment that gives the lowest chi2 of the muon+jets selected sample for an integrated luminosity of 36/pb after applying the event selection. GIF
Top quark mass before the fit of the muon+jets selected sample for an integrated luminosity of 36/pb after applying the event selection and requesting at least one solution with chi2<10. GIF
Top quark mass after the fit of the muon+jets selected sample for an integrated luminosity of 36/pb after applying the event selection and requesting at least one solution with chi2<10. GIF
Uncertainty on the fitted top mass of the muon+jets selected sample for an integrated luminosity of 36/pb after applying the event selection and requesting at least one solution with chi2<10. GIF
WrongCombination_el.gif Shape of the fitted masses for the wrong jet permutations, from ttbar simulation with mt=172.5 GeV, in the electron+jets channel. GIF
WrongCombination_mu.gif Shape of the fitted masses for the wrong jet permutations, from ttbar simulation with mt=172.5 GeV, in the muon+jets channel.GIF
M3.gif M3, the invariant mass of the system of 2 untagged jets and one b-tagged jet that yields the vectorial sum with highest pT in data and MC (with mt=172.5 GeV, JES=1) in the muon+jets channel. GIF
M2.gif M2, the mass of the 2 untagged assigned to M3, in data and MC (with mt=172.5 GeV, JES=1) in the muon+jets channel. GIF
deltaM32.gif Mass difference M3-M2, in data and MC (with mt=172.5 GeV, JES=1) in the muon+jets channel.GIF
3masses.gif Example of masses fitted in pseudo-experiments for three generated values of the top mass: 166.6, 172.5 and 178.5 GeV, using W+jets simulation to represent the background. GIF
pull.gif Pull distribution for the pseudo-experiments obtained with the central sample with mt=172.5 GeV, using W+jets simulation to represent the background. GIF
bias_vs_mass.gif Difference between the mean fitted and generated top mass in pseudo-experiments, as a function of the top mass, for the combined lepton+jets channel. GIF
pull_vs_mass.gif Width of the fitted mass pull as a function of the generated top mass, for the combined lepton+jets channel. GIF
likelihood_el.gif Overall log-likelihood for all events selected in the electron+jets channel, as function of the top mass. GIF
expected_error_el.gif Statistical uncertainty observed in data, compared to the distribution of statistical uncertainties in pseudo-experiments, for the electron+jets channel. GIF
likelihood_mu.gif Overall log-likelihood for all events selected in the muon+jets channel, as function of the top mass. GIF
expected_error_mu.gif Statistical uncertainty observed in data, compared to the distribution of statistical uncertainties in pseudo-experiments, for the muon+jets channel. GIF
likelihood_combined.gif Overall log-likelihood for all events selected in the combined lepto+jets channel, as function of the top mass. GIF
expected_error_combined.gif Statistical uncertainty observed in data, compared to the distribution of statistical uncertainties in pseudo-experiments, for the combined lepton+jets channel. GIF
M2fit.gif M2 template fitted to the data, in the muon+jets channel. GIF
deltaM32fit.gif (M3-M2) mass difference template fitted to the data, in the muon+jets channel. GIF
ellipse.gif The 68% confidence region in the mt-JES plane, extracted from the template fit, in the muon+jets channel. GIF
comparison.gif Comparison of the distributions of the expected statistical uncertainty of the ideogram analysis, applying successively various simplifications of the analysis, with the statistical uncertainty observed in data for the default ideogram analysis and the cross-check analysis. GIF
ideogram_a.gif Example of an ideogram event likelihood as function of the top mass, for an event with 0 b-tagged jets.GIF
ideogram_b.gif Example of an ideogram event likelihood as function of the top mass, for an event with 0 b-tagged jets.GIF
ideogram_c.gif Example of an ideogram event likelihood as function of the top mass, for an event with 1 b-tagged jet.GIF
ideogram_d.gif Example of an ideogram event likelihood as function of the top mass, for an event with 1 b-tagged jet. GIF
ideogram_e.gif Example of an ideogram event likelihood as function of the top mass, for an event with 1 b-tagged jet.GIF
ideogram_f.gif Example of an ideogram event likelihood as function of the top mass, for an event with 1 b-tagged jet.GIF
ideogram_g.gif Example of an ideogram event likelihood as function of the top mass, for an event with 2 or more b-tagged jets.GIF
ideogram_h.gif Example of an ideogram event likelihood as function of the top mass, for an event with 2 or more b-tagged jets.GIF

Tables from TOP-10-009 ( click on plot to get .png )

Result Abbreviated Caption
Table1.png Event yields in data and MC simulation for the various contributing processes after all selection steps except the requirement of a solution of the kinematic fit with chi2<10 for at least one of the possible jet assignment hypotheses.
Table2.png Overview of systematic uncertainties considered.
Table3.png CMS results for the top mass and corresponding measurement uncertainties, for the lepton+jets and di-lepton channels and their combination, in GeV.

-- MartijnMulders - 06-Jun-2011

Topic attachments
I Attachment History Action Size Date Who Comment
GIFgif 3masses.gif r1 manage 35.9 K 2011-06-07 - 13:32 MartijnMulders  
PNGpng CombinedResult.PNG r1 manage 5.7 K 2011-06-07 - 17:34 MartijnMulders  
GIFgif M2.gif r1 manage 31.4 K 2011-06-07 - 13:13 MartijnMulders  
GIFgif M2fit.gif r1 manage 38.7 K 2011-06-07 - 13:37 MartijnMulders  
GIFgif M3.gif r1 manage 32.0 K 2011-06-07 - 13:12 MartijnMulders  
PNGpng Table1.png r1 manage 39.3 K 2011-06-07 - 18:31 MartijnMulders  
PNGpng Table2.png r1 manage 72.3 K 2011-06-07 - 18:32 MartijnMulders  
PNGpng Table3.png r1 manage 103.7 K 2011-06-07 - 18:32 MartijnMulders  
PNGpng TheMainResult.PNG r1 manage 5.8 K 2011-06-07 - 17:33 MartijnMulders  
GIFgif WrongCombination_el.gif r1 manage 24.1 K 2011-06-07 - 13:12 MartijnMulders  
GIFgif WrongCombination_mu.gif r1 manage 24.7 K 2011-06-07 - 13:12 MartijnMulders  
GIFgif bias_vs_mass.gif r1 manage 38.2 K 2011-06-07 - 13:33 MartijnMulders  
GIFgif comparison.gif r1 manage 48.2 K 2011-06-07 - 13:39 MartijnMulders  
GIFgif deltaM32.gif r1 manage 31.2 K 2011-06-07 - 13:13 MartijnMulders  
GIFgif deltaM32fit.gif r1 manage 37.2 K 2011-06-07 - 13:38 MartijnMulders  
GIFgif e_h4ji_fitChi2Min.gif r1 manage 13.8 K 2011-06-07 - 11:45 EnriquePalencia  
GIFgif e_h4ji_fittedTopMass.gif r1 manage 16.2 K 2011-06-07 - 11:46 EnriquePalencia  
GIFgif e_h4ji_fittedTopMassSigma.gif r1 manage 16.9 K 2011-06-07 - 11:46 EnriquePalencia  
GIFgif e_h4ji_jet0nBTag.gif r1 manage 14.5 K 2011-06-07 - 11:46 EnriquePalencia  
GIFgif e_h4ji_met.gif r1 manage 16.7 K 2011-06-07 - 11:46 EnriquePalencia  
GIFgif e_h4ji_unfittedTopMass.gif r1 manage 17.1 K 2011-06-07 - 11:47 EnriquePalencia  
GIFgif ellipse.gif r1 manage 31.3 K 2011-06-07 - 13:38 MartijnMulders  
GIFgif expected_error_combined.gif r1 manage 34.2 K 2011-06-07 - 13:37 MartijnMulders  
GIFgif expected_error_el.gif r1 manage 35.4 K 2011-06-07 - 13:35 MartijnMulders  
GIFgif expected_error_mu.gif r1 manage 35.2 K 2011-06-07 - 13:36 MartijnMulders  
GIFgif ideogram_a.gif r1 manage 19.7 K 2011-06-07 - 13:39 MartijnMulders  
GIFgif ideogram_b.gif r1 manage 18.7 K 2011-06-07 - 13:40 MartijnMulders  
GIFgif ideogram_c.gif r1 manage 19.3 K 2011-06-07 - 13:40 MartijnMulders  
GIFgif ideogram_d.gif r1 manage 21.0 K 2011-06-07 - 13:41 MartijnMulders  
GIFgif ideogram_e.gif r1 manage 21.3 K 2011-06-07 - 13:41 MartijnMulders  
GIFgif ideogram_f.gif r1 manage 22.9 K 2011-06-07 - 13:42 MartijnMulders  
GIFgif ideogram_g.gif r1 manage 19.8 K 2011-06-07 - 13:42 MartijnMulders  
GIFgif ideogram_h.gif r1 manage 22.6 K 2011-06-07 - 13:42 MartijnMulders  
GIFgif likelihood_combined.gif r1 manage 21.2 K 2011-06-07 - 13:36 MartijnMulders  
GIFgif likelihood_el.gif r1 manage 21.5 K 2011-06-07 - 13:34 MartijnMulders  
GIFgif likelihood_mu.gif r1 manage 21.4 K 2011-06-07 - 13:35 MartijnMulders  
GIFgif mu_h4ji_fitChi2Min.gif r1 manage 13.9 K 2011-06-07 - 11:47 EnriquePalencia  
GIFgif mu_h4ji_fittedTopMass.gif r1 manage 16.1 K 2011-06-07 - 11:47 EnriquePalencia  
GIFgif mu_h4ji_fittedTopMassSigma.gif r1 manage 16.6 K 2011-06-07 - 12:11 EnriquePalencia  
GIFgif mu_h4ji_jet0nBTag.gif r1 manage 14.3 K 2011-06-07 - 11:47 EnriquePalencia  
GIFgif mu_h4ji_met.gif r1 manage 16.9 K 2011-06-07 - 11:48 EnriquePalencia  
GIFgif mu_h4ji_unfittedTopMass.gif r1 manage 16.8 K 2011-06-07 - 11:48 EnriquePalencia  
GIFgif pull.gif r1 manage 32.6 K 2011-06-07 - 13:33 MartijnMulders  
GIFgif pull_vs_mass.gif r1 manage 36.1 K 2011-06-07 - 13:34 MartijnMulders  
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Topic revision: r6 - 2011-06-07 - MartijnMulders
 
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